With spectrum remaining a scarce communication resource, different types of communication networks increasingly operate in and compete for usage of the same or overlapping spectrum. Consider, for example, the case of using “license assisted access” or LAA in the context of Wireless Wide Area Networks or WWANs that are based on the Long Term Evolution, LTE, specifications promulgated by the Third Generation Partnership Project, 3GPP.
LTE with LAA aggregates carriers in the licensed spectrum with carriers in shared or unlicensed spectrum—e.g., the LTE network serves a given wireless communication device using a primary carrier in licensed spectrum and a secondary carrier in the 5 GHz unlicensed spectrum. This approach takes advantage of the presence of relatively large amounts of spectrum in the unlicensed spectrum (such as between 5.150 GHz and 5.350 GHz).
Note that the same approach can be applied to Licensed Shared Access (LSA) and Authorized Shared Access (ASA) spectrum. LSA and ASA are approaches whereby spectrum licensed to an incumbent wireless operator may also be used by other licensees or authorized users when not in use by the incumbent wireless operator.
FIG. 1 depicts an example arrangement, where a LTE network 6 serves a User Equipment, UE, 8 using a Carrier Aggregation, CA, configuration that aggregates a primary carrier in the network's licensed spectrum with a second carrier in shared or unlicensed spectrum. This approach allows the LTE network 6 to boost data speeds to the UE 8 and to better manage loading in the licensed spectrum. Usage of shared or unlicensed spectrum may be conditioned on need, such as in dependence on the communication service or services being used by the UE 8 and/or on the number of users, loading in the licensed spectrum, etc.
Of course, other types of networks or systems may be operating in the shared or unlicensed spectrum, and co-existence with these other networks represents a key aspect of fairly sharing the shared or unlicensed spectrum. Wireless Local Access Networks, WLANs, based on the IEEE 802.11 standards—popularly known as Wi-Fi networks—are significant users of unlicensed spectrum, although networks based on still other Radio Access Technologies, RATs, may operate in the shared or unlicensed spectrum of interest to the network operator.
In the particular example context of a LTE network sharing spectrum with one or more Wi-Fi networks, one might consider the LTE network as “fairly” sharing the same spectrum used by Wi-Fi if its usage of that spectrum does not affect Wi-Fi services in the involved coverage area(s) to any greater extent than they would be affected by adding an additional Wi-Fi network on the same carrier.
Regardless of how one measures “fair” use, it will be appreciated that a licensed network should “coexist” as well as possible with any networks operating in the same shared or unlicensed spectrum targeted by the licensed network for supplementing its licensed spectrum. Various coexistence mechanisms are known, but they can be broadly understood as controlling channel selection and channel usage. For example, a base station in a licensed network may activate and use secondary carriers in a shared or unlicensed spectrum based on finding the “cleanest” channel or channels in the shared or unlicensed spectrum.
The base station might, for example, perform a series of interference measurements in the frequencies corresponding to the set of channels within all or a portion of the shared or unlicensed spectrum. It also may be required for the network to perform a Listen-Before-Talk, LBT, operation before transmitting on a channel in the shared or unlicensed spectrum.
To some extent, the UEs or other wireless devices being supported by the wireless network may provide helpful information to the network, e.g., by providing inter-RAT measurements to the network. For example, it is known to have LTE UEs provide at least a limited set of Wi-Fi related measurements to the LTE network, to improve the coexistence mechanisms of the LTE network. For example, certain Wi-Fi Access Points, APs, may be visible to nearby UEs, but not visible to or otherwise detectable by the LTE base stations serving the UEs.
Broadly, many challenges remain with respect to improving these coexistence mechanisms, as the use of shared or unlicensed spectrum becomes more prevalent.